US EPA Air Quality data, 1972-1988

U.S. Environmental Protection Agency air pollution monitoring data from 1972 through 1988 consist of raw, monitor-level observations for sulfur dioxide (SO₂), total suspended particulates (TSP), nitrogen dioxide (NO₂), ozone (O₃), and carbon monoxide (CO), obtained directly from the EPA. SO₂ measurements typically reflect sample durations of about one hour, while other pollutants are reported according to contemporaneous EPA monitoring practices, with substantial variation in sampling frequency and spatial coverage across pollutants and years. SO₂ has the broadest and most consistent coverage, with thousands of monitors operating in over 1,000 counties, whereas TSP is measured less frequently, O₃ data are largely unavailable prior to 1980, NO₂ coverage declines by the late 1980s, and CO data become widely available starting in the mid-1970s. The provided .do file serves as an example for how to process the provided datasets into a daily monitor-level dataset.